(JTA) – Israel’s main state museum and research body on the Holocaust said Thursday that a joint statement by Israel and Poland on the genocide contained “grave errors and deceptions.”

The Yad Vashem statement pertains to a declaration made last week by Israeli Prime Minister Benjamin Netanyahu and his Polish counterpart, Mateusz Morawiecki, that acknowledges collaboration by some Poles during the Holocaust and the rescue of Jews by others. It also states that during the Holocaust, “unfortunately, the sad fact is that some people – regardless of their origin, religion or worldview – revealed their darkest side.”

Newspapers in Israel, Germany and the United Kingdom published the declaration, leading to criticism from opposition leaders and historians in Israel. The PKO Foundation of Poland’s Bank Polski paid for the ads. The bank has close ties to the government.

Beyond the “outrageous insinuation that Jews also revealed ‘their darkest side at that time,’” Yad Vashem wrote, the Poles who revealed it “were not devoid of identity.”

The joint declaration was designed to end the diplomatic spat between Poland and Israel over a law passed in Poland’s parliament in February that criminalized blaming the Polish nation for Nazi crimes. Israel protested the law and Poland’s government subsequently softened it, adding an amendment that scraps the three-year prison sentence prescribed in the original legislation.

Yad Vashem’s chief historian, Dina Porat, accompanied the work of Polish and Israeli diplomats who hammered out the declaration finalizing the détente, Netanyahu said. Yad Vashem said last week that the amendment was “a positive development in the right direction.”

But on Thursday, the museum apparently changed its position, citing “a thorough review by Yad Vashem historians” of the joint declaration published on June 27.

The joint declaration “contains highly problematic wording that contradicts existing and accepted historical knowledge in this field,” the statement said. The document’s wording “effectively supports a narrative that research has long since disproved, namely, that the Polish government-in-exile and its underground arms strove indefatigably – in occupied Poland and elsewhere – to thwart the extermination of Polish Jewry.”

Last week, Yad Vashem’s academic adviser, Yehuda Bauer, said in a radio interview that the joint declaration was a “betrayal” by Israel of “the wonderful Polish liberals” who may be exposed to litigation in civil court under the law passed by the country’s right-wing government.